Progress 10/01/98 to 09/30/03
Outputs
Investigations conducted during the project included assessing the attachment and penetration of conidia of the parasitic fungus, Hirsutella rhossiliensis, to larvae of the northern root-knot nematode; effects of cultural practices (rotation, cover crops, compost and green manures, organic production) on root disease severity; and the mechanism by which green manures of sudangrass hybrids suppress nematodes and their damage. In 2003, the incorporation of a green manure of sudangrass did not reduce bean root rot severity or increase yield in a heavy-textured soil with high infestations of root pathogens (Fusarium, Pythium, Rhizoctonia and Thielaviopsis). Also, sealing the soil immediately after the incorporation of the green manure did not result in better yield or reduced root rot severity. Additional cycle(s) of green manure applications might be required before reduction in root rot severity and an increase in bean yield can be realized under such high infestation
levels with root pathogens. Seed treatment of tomato with a special formulation of Abamectin (total fermentation products of Streptomyces avermilitis) was effective in reducing the number of juveniles of Meloidogyne hapla penetrating roots when determined at 2 weeks after planting. In greenhouse tests, root-galling severity ratings and eggs production on roots were also reduced by the Abamectin seed treatment. Similarly, the Abamectin seed treatment reduced the number of Pratylenchus penetrans in tomato roots. Ten, long-term demonstrations sites of a collaborative project on soil health were assessed for their root rot disease potential and diversity of plant-parasitic and free-living nematodes. The data obtained clearly illustrated that these sites differed greatly in their disease potential as determined by soil bioassay with beans in the greenhouse and also in the number and diversity of nematodes. The evaluation of the data and its correlation to various management options and
soil physical and chemical measurements is on-going.
Impacts
Documenting the efficacy of biological products against soilborne pathogens under controlled and production conditions will contribute to the development of IPM and biologically-based control programs. Understanding the impact of cultural practices on soilborne pathogens, damage of root diseases and soil biology in general is critical in developing sustainable control options against soilborne pathogens that are also compatible with practices required for maintaining soil health and productivity.
Publications
- Widmer, T. L., N. A. Mitkowski, and G. S. Abawi. 2002. Soil organic matter and management of plant-parasitic nematodes. J. of Nematology 34:289-295.
- Abawi, G. S., and J. W. Ludwig. 2002. Management of bean root rots by cultural practices. Bean Improvement Cooperative 45: 40-41.
- Abawi, G.S., J. W. Ludwig, H. V. Morton, and D. Hofer. 2003. Efficacy of Abamectin as a seed treatment against Meloidogyne hapla and Pratylenchus penetrans. J. of Nematology 35: 321 (Abstr.).
- Carroll, J. E., P. Chen, and G. S. Abawi. 2003. Demonstrating the effectiveness of an IPM profram for the management of leaf blight diseases of carrots in New York. Phytopathology 93 (suppl.): 14 (Abstr.).
|
Progress 01/01/02 to 12/31/02
Outputs
The effects of green manures of 10 crops (alfalfa, sudangrass, wheat, buckwheat, ryegrain, bahiagrass, ryegrass, or beans) and two composts (chicken or cow manures) on the severity of Rhizoctonia root rot of beans were evaluated in the greenhouse. All the treatments reduced the severity of root rot, as compared to the treatment planted to beans (check). The lowest root rot severity was observed on beans planted after alfalfa. Interestingly, beans grown in the fallow check treatment also exhibited low root rot severity. The highest growth weight of beans was observed in the field corn and sudangrass treatments, which they also exhibited low root rot severity. A total of 20 beet fields were monitored for the development of pocket rot, caused by R. solani and their soil samples were also indexed through greenhouse and laboratory tests. The objective of the later was to validate a procedure for assessing the need for control options prior to planting. Due to the extreme
dry and hot weather, pocket rot did not develop to a measurable level in 19 out of the 20 fields. Disease developed (2.5 percent) in one field that has been cropped extensively to vegetables. The results of the bioassays with beets and beans as well as the trapping of Rhizoctonia with beet seeds showed differences among the fields, but results of the three tests were not correlated positively with each other. The greenhouse bioassay with beets appears as the most reliable detection method. Fields that were rotated to grain crops, planted to a cover crop or received animal manure applications generally yielded lower recovery of Rhizoctonia.
Impacts
The influence of rotational, cover crops and other production inputs on population and damage of soilborne pathogens will contribute to the development of biologically based control options. Assessing the potential development of root diseases will avert crop losses and implementation of appropriate control options.
Publications
- Widmer, T. L., and Abawi, G. S. 2002. Relationship between levels of cyanide in sudangrass hybrids incorporated into soil and suppression of meloidogyne hapla. J. of Nematology 34:16-22.
- Abawi, G. S., and Ludwig, J. W. 2003. Comparing the effectiveness of selected cover crops incorporated as green manures without and with a surface seal against root pathogens of beans/vegetables. NYS IPM Publication No. 129, pp 67-71, NYSAES, Geneva, NY. 183 pp.
|
Progress 01/01/01 to 12/31/01
Outputs
Conidia of Hirsutella rhossiliensis were found to readily attach to the surface of nematodes by the mucilaginous layer that surrounds each conidium. Attached spores of H. rhossiliensis develop germ tubes and by 24 hours have penetrated the nematode cuticle. Infected nematodes often live and exhibit vigorous movements up to 40 hours after attachment of the conidia (and, approximately 20 hours after being invaded by the fungus). By 96 hours, the nematode body is fully occupied by hyphae of the pathogen. Root rot severity ratings of 27 dry bean fields varied from 1.1 to 6.9 in a greenhouse bioassay test on a scale of 1 (no disease symptoms) to 9 (>75% of root and stem tissues affected with considerable decay). The actual root rot severity developed on beans grown in the same fields varied between 2.0 and 5.9. Populations of lesion and root-knot nematodes as well as non-parasitic nematodes also varied among the fields, but did not appear to follow the root rot severity
ratings. Beans grown following a grain crop exhibited lower root rot severity ratings than beans grown after bean or other vegetables. The eight fields that had a root rot rating of <5 by the bioassay procedure, have been out of bean production for 3 years and mostly in grain crops (corn, wheat or spelt). However, growing grain crops prior to beans appear to increase the number of lesion nematodes in soil and roots. Surprisingly, the use of non-composted animal manures increased root rot severity, but suppressed the number of lesion nematodes in bean roots. Preparations of Trichoderma harzianum (T-22) and Kodiak (Bacillus subtilis) were ineffective as seed treatments in controlling seed and seedling diseases of beans in a heavily infested field with root rot pathogens.
Impacts
The findings on the parasitism of Hirsutella rhossiliensis are useful in that they set time lines for the infection process as well as for the mode on fungal ingress into the nematode body. Knowledge on the effects of cultural practices and production inputs on the incidence and damage of soilborne pathogens is critical in the development of control options of root diseases that are compatible with sustainable management of soil health and productivity. It is also important to validate the efficacy of available commerical preparations in different soils and production systems, as their activities might well be different.
Publications
- Widmer, T.L., and Abawi, G.S., 2000. Mechanism of suppression of the northern root-knot nematode by sudangrass incorporated as a green manure. Plant Disease 84: 562-568.
- Widmer, T.L., and Abawi, G.S., 2001. Relation between levels of cyanide of sudangrass bybrids incorporated into soil and suppression of Meloidogyne hapla. J. of Nematology 33: (Accepted).
- Widmer, T.L., Mitkowski, N.A., and Abawi, G.S., 2001. Soil organic matter and management of plant-parasitic nematodes. J. of Nematology 33: (Accepted).
|
Progress 01/01/00 to 12/31/00
Outputs
Using lectin-affinity labeling, it was determined that the mucilaginous layer surrounding the spores of Hirsutella rhossiliensis is complex and consist of at least a-mannans, a-glucans, and N-acetylglucosamine. Once the spores make contact with a surface the glue-like mucilage spreads from the spore. Adhesion of the spores to substrata appears to be non-specific with regard to surface wettability. Over a period of 1-6 hours the layer partially dissolves, however, most of it remains present as the spores begin germination. Immediately upon germination a bulbous swelling develops (unlike an appressorium) that is probably equivalent to the 'infection bulb' observed in infected nematodes. The prevalence and damage of soilborne pathogens as well as soil suppressiveness have been monitored in organic and conventional vegetable production systems. High marketable yield (fresh pod weight) of snap beans (>6 T/A) was obtained in plots fertilized with the standard rate of
chemical fertilizer or the dry poultry compost. Only slightly lower root rot severity was observed on plants growing in the plots receiving the poultry compost and the chemical fertilizer, as compared to plants growing in the non-fertilized plots. Agri-Mek 0.15 EC (Abamectin, fermentation products of Streptomyces avermitilis) applied as a drench treatment at a rate of 16 oz./A, but not at 8 oz./A, was effective in reducing root galling severity and damage caused by Meloidogyne hapla on tomatoes.
Impacts
(N/A)
Publications
- Abawi, G. S., and Widmer, T. L.. 2000. Impact of soil health management practices on soilborne pathogens and root diseases of vegetable crops. Applied Soil Ecology 15: 37-47.
- Abawi, G. S., and Ludwig, J. W. 2000. Bean root rot management results, 1999: Varieties, seed treatments, cover crops, and composts. NYS Veg. Conf., pp. 36-39, Cornell Cooperative Extension, Ithaca, NY.
- Abawi, G. S., and Ludwig, J. W. 2000. Pocket rot disease of beets and its management. NYS Veg. Conf., pp. 47-50, Cornell Cooperative Extension, Ithaca, NY.
- Viaene, N. M., and Abawi, G. S. 2000. The fungi Hirsutella rhossiliensis and Verticillium chlamydosporium as biocontrol agents of the root-knot nematode, Meloidogyne hapla, on lettuce. J. of Nematology 32: 85-100.
- Widmer, T.L., and Abawi, G.S. 2000. Impact of organic matter management on plant-parasitic nematodes, their damage to host crops, and soil health. J. of Nematology 32 (Abstr., in-press)
|
Progress 01/01/99 to 12/31/99
Outputs
It was previously documented that spores of Hirsutella rhossilienses produced in situ (soil) readily infected plant - parasitic nematodes, but not isolated spores from culture media. It was found that the adhesive material which surrounds the spores does not adhere the spores to either hydophobic or hydrophilic surfaces when a thick water layers is present. A number of organic soils cropped to onions and other vegetables were found to be with below detection or with low density of the root-knot nematode (Meloidogyne hapla). Greenhouse tests with and without additional infestation by M. hapla in pasteurized and non-treated samples of these soils confirmed the observed suppressive nature of these soils against M. hapla. The efficacy of green manures of several accessions of flax and white clover against M. hapla on lettuce was significantly reduced by the green manures of the cyanogenic flax and white clover selections, but not by the non-cyanogenic white clover
included in the test. The two long-term experiments on the effects of cultural practices (cover crops, composts, tillage, and rotation) on root rot severity and yield of beans were continued during the 1999 season, which was unusually dry and warm. Results obtained did not show the beneficial effects obtained in previous years for green manures, composts, and tillage. For example, yield of beans in the fallow plots was greater than the yield of beans in the plots with cover crops. The latter was due to the delay in emergence of beans in the plots with the cover crops due to lower soil moisture. These results document the special management efforts needed for biologically based control options. For example, the cover crops should have been incorporated 4 to 6 weeks earlier in order to retain the soil moisture during the unusual dry weather that prevailed in 1999.
Impacts
(N/A)
Publications
- Abawi, G. S., Widmer, T. L., and Ludwig, J. W. 1999. Effects of cultural practices on bean root rot and its management. Phytopathology (Suppl.) 89:S1.
- Abaw, G. S., and Widmer, T. L. 2000. Impact of soil health management practices on soilborne pathogens and root diseases of vegetable crops. Applied Soil Ecology 7: (in-press).
- Widmer, T. L., and Abawi, G. S. 1999. Concentration of cyanide in various sudangrass cultivars correlated to suppression of Meloidogyne hapla. Phytopathology 88:S97.
- Viaene, N. M., and Abawi, G. S. 2000. The fungi Hirsutella rhossiliensis and Verticillium chlamydosporium as biocontrol agents of the root-knot nematode, Meloidogyne hapla, on lettuce. J. of Nematology 32: (in-press).
|
Progress 01/01/98 to 12/31/98
Outputs
The emulsifiable solution (ES), but not the aqueous solution formulation, of the biological nematicide DiTera reduced the number of Pratylenchus penetrans in bean roots. Two applications of DiTera at the lowest rate tested (47.3 L/Ha) resulted in significantly fewer nematodes per gram roots. Neither formulations of DiTera exhibited activity against Meloidogyne hapla on lettuce in both organic and mineral soils. However, the ES formulation reduced top and root weight of bean seedlings. Results obtained on the mechanism of suppression of M. hapla and its damage to onions, lettuce and carrots by green manures of sudangrass indicate that the primary factor is decomposition by-products of the cyanogenic glucoside, dhurrin, which is present in the epidermal cells of sudangrass. P-hydroxymandelonitrite and HCN were highly effective and at low concentrations against eggs of M. hapla, whereas dhurrin and p-hydroxybenzaldehyde were in-effective. However, soil respiration and
total counts of fungi, bacteria, and nematodes were found to be higher in soils amended with sudangrass and wheat as compared to those amended with oat or chitin and non-amended soils, thus suggesting a possible role of increased microbial activities in nematode suppression. Sub-soiling the previous fall resulted in significant increase in plant population and yield of the succeeding bean crop, but it had no effect on root rot severity. A 2-year rotation out of beans (sweet corn for 2 years or table beet and sweet corn) significantly increased bean yield and slightly reduced root rot severity. In the continuous bean rotation, a previous cover crop of rye resulted in the highest bean yield and lowest root rot severity. In contrast, lowest yield and highest root rot severity were obtained when beans followed a cover crop of hairy vetch.
Impacts
(N/A)
Publications
- Widmer, T. L., and G. S. Abawi. 1998. Suppressive mechanism of sudangrass incorporated as a green manure against Meloidogyne hapla. Phytopathology 88: S97.
- Viaene, N, M., and G. S. Abawi. 1998. Fungi parasitic on juveniles and egg masses of Meloidogyne hapla in organic soils from New York. Suppl. J. of Nematology 30: (in-press).
|
Progress 01/01/97 to 12/31/97
Outputs
System 3, a seed treatment formulation of Bacillus subtilis and the fungicides Terrachlor and Metalaxyl, protected untreated bean seeds from damage by root rot pathogens when used as a dust or slurry treatment. However, no benefit was evident when System 3 was applied to bean seeds commercially treated with the recommended fungicides, Captan and Metalaxyl. The granular and wettable formulations of Soilgard (Gliocladium virens), Strain T-22 of Trichoderma harzianum, and olive oil were ineffective in suppressing root rot diseases of beans and their damage. Similarly, formulations of Deny (Psuedomonas cepacia) and humic acids were ineffective in reducing infections by the northern root-knot nematode (Meloidogyne hapla) on lettuce and lesion nematode (Pratylenchus penetrans) on beans. A cover crop of a mixture of ryegrain and hairy vetch incorporated as a green manure significantly increased pod yield of beans, although it did not affect seedling establishment and root
rot severity under the relatively dry weather conditions that prevailed during the test. In greenhouse tests, maintaining the soil wet after the incorporation of ryegrain resulted in poor seedling establishment, poor growth, and increased root rot severity. Damage to beans was especially severe when beans were planted 1 or 2 weeks after the ryegrain incorporation under wet conditions. However, waiting 4 weeks before planting beans resulted in improved emergence and plant growth as well as reduced root rot severity. The damage to beans under wet condition in soil amended with green manure of ryegrain may be due to increased activities of root pathogens or the release of toxic decomposition products. In another greenhouse test, several cover crops including ryegrass, rapeseeds, wheat, sudangrass, oat, and crown vetch significantly reduced root rot severity and increased bean growth.
Impacts
(N/A)
Publications
- Abawi, G. S. 1998. Snap bean rotations, cover crops and root rot management. Proc. NYS Vegetable Conference, Cornell Cooperative Extension. 2 pp.
- Pyndji, M., G. S. Abawi, and R. Buruchara. 1997. Use of green manures in suppressing root rot severity and damage to beans in Uganda. Phytopathology 87 (Suppl.): 80 (Abstr.).
|
Progress 01/01/96 to 12/30/96
Outputs
An isolate of the nematode-trapping fungus, Arthrobotrys dactyloides obtained from organic soil in New York, was found effective in reducing penetration of juveniles of root-knot nematode, Meloidogyne hapla, into roots of lettuce seedlings when it was introduced into soil as alginate pellets or colonized wheat bran. The parasite was also found compatible with the use of sudangrass as a green manure. Under severe root rot pressure, the addition of spores of Trichoderma harzianum strain 22 to bean seeds with and without the fungicide Captan did not improve seedling establishment, reduce root rot severity or increase yield under field conditions. Similarly, the other biological control treatments that were field tested such as Gliocladium virens, Laetisaria arvalis and clove oil did not exhibit a beneficial effect on beans. In a greenhouse tests, bean growth was increased and root rot severity was reduced with the application of a green manure of alfalfa, crown vetch,
oat, rapeseed, ryegrain, ryegrass, sudangrass, wheat, white clover, or white mustard. In a large field test, a cover crop of ryegrain reduced bean yield under the severe root rot and wet weather conditions that prevailed during the growing season. However, the application of a brewery compost increased bean yield and reduced root rot severity. The addition of chicken compost at 5 tons/A increased yield and reduced the percentage of unmarketable table beets, but not those of beans and sweet corn.
Impacts
(N/A)
Publications
- Abawi, G. S., and Ludwig, J. W. 1996. Host range of a tumorigenic strain of Erwinia herbicola from table beets. Phytopathology 86 (No. 11, supplement): 3 (Abstr.).
- Abawi, G. S. 1996. Root diseases of beans. Proc. NYS Vegetable Conference, Cornell Cooperative Extension, Ithaca, NY. pp. B 11-14.
- Jaffee, B. A., Abawi, G. s., Muldoon, A. E., and Westerdahl, B. B. 1995. Efficacy of palletized hyphae of Hirsutella rhossiliensis against Heterodera schachtii in field microplots. J. Nematology 27:504 (Abstr.).
- Olaya, G., Abawi, G. S., and Weeden, N. F. 1996. Inheritance of the resistance to Macrophomina phaseolina and identification of RAPD markers linked to the resistance genes in beans. Phytopathology 86:674-679.
- Olaya, G., and Abawi, G. S. 1996. Effect of water potential on mycelial growth, and on production and germination of sclerotia of Macrophomina phaseolina. Plant Disease 80:1347-1350.
- Olaya, G., and Abawi, G. S. 1996. Influence of water potential on survival of sclerotia in soil and infection of beans by Macrophomina phaseolina. Plant Disease 80:1351-1354.
|
Progress 01/01/95 to 12/30/95
Outputs
A spore preparation of Trichoderma harzianum strain 22 was applied to snap bean seeds with and without the recommended fungicide seed treatment of Apron + Demosan. The four treatments were field evaluated in an experimental root rot field under commercial production practices. Seed application of Trichoderma increased stand establishment and pod weight in plots where seeds untreated with fungicides were used, but not in those planted with the recommended fungicide-treated seeds. Results of greenhouse tests suggested that Trichoderma had little effect against Thielaviopsis root rot of beans. Several tests were initiated to determine the efficacy of cover crops incorporated as green manures in suppressing soilborne pathogens of vegetables. The incorporation of sudangrass in fall, 1994 resulted in reduction of root rot severity and higher fresh weight of peas at bloom time. Also, plant establishment and marketable weight of peas were higher in the sudangrass plots, but
the differences were not significant. In greenhouse tests, the number of lesion nematode (Pratylenchus penetrans) were lowest in roots of beans after a green manure of ryegrass, sudangrass, and rapeseed; but were highest after a green manure of hairy vetch. In large field tests, yield of snap beans was increased and root rot severity was decreased with the application of brewery compost or corn silage. Results of another test indicated that bean yield was highest and root rot severity was lowest in plots that were deep-tilled and re.
Impacts
(N/A)
Publications
|
Progress 01/01/94 to 12/30/94
Outputs
The antagonist Hirsutella rhossiliensis (Hr) was effective in reducing penetration of J2 of Heterodera schachtii into roots of table beets in pasteurized soils, but not in natural soils under field microplot conditions. The greatest colony diameter of Hr originating from a single alginate pellet averaged 8.1 mm after two week incubation in pasteurized soil, but similar colonies were often not observed or averaged <0.2 mm in natural soils. It appears that the alginate pellets of Hr in natural soils are suppressed by soil microorganisms and/or consumed by soil arthropods, collembola and enchytreads. Nine binucleate isolates of Rhizoctonia were previously documented in greenhouse tests to significantly reduce infections of R. solani and increase dry weight of table beet seedlings. A field test was conducted in 1994 to evaluate the efficacy of one of these binucleate isolates (#592) in reducing foliar and root infections of R. solani. Inocula of both the binucleate isolate
and R. solani consisted of the soil-potato inoculum preparation. Two-month old beets were inoculated with the binucleate and/or the R. solani isolates using 100 cc/m row. Prior inoculation of table beets with the binucleate isolate resulted in significant reduction in the incidence and severity of foliar and root infections of R. solani and increased yield of marketable beets. The binucleate isolate was effective when applied simultaneously or 2 and 5 days prior to inoculations with R. solani.
Impacts
(N/A)
Publications
|
Progress 01/01/93 to 12/30/93
Outputs
About 35 and 85 percent of J2 of Meloidogyne hapla (Mh) became infected when exposed to Hirsutilla rhossiliensis (Hr) in soil and on culture plates, repectively. The number of J2 of Mh that penetrated lettuce roots was decreased as the number of Hr colonies added to the soil was increased from 75 to 700 colonies/cc soil. Penetration of J2 of Heterodera schachtii (Hs) into roots of table beets growing in field microplots was decreased as the number of colonies of Hr in soil was increased in 3 of the 5 experiments. The addition of Hr at a rate of 10 g (about 16950 colonies)/7500 cc soil did not prevent the reduction in yield of table beets caused by Hs (20 eggs/cc soil). Nine binucleate isolates of Rhizoctonia significantly reduced the percentage of table beet seedlings infected with R. solani (Rs) and increased dry weight. The binucleate isolates were effective in reducing seed decay and seedling infection when they were applied as hyphal fragments to seeds with
methylcellulose, or mixed into the soil as colonized beet seedballs or infested soil-potato inoculum preparation. The binucleate isolates were effective when used with untreated or Apron+Thiram-treated seeds. Incorporation of a cover crop, Trudan 8, did not affect the stand, yield, or root rot severity of beans. Bioassay of soil samples in the greenhouse showed no differences between the trudan 8 and the fallow plots.
Impacts
(N/A)
Publications
|
Progress 01/01/92 to 12/30/92
Outputs
Two strains of Pseudomonas cepacia (Blue Circle, provided by Stine Microbial Products, Madison, WI) and strain AB254 of Ps. fluorescens (provided by Dr. Nancy Callan, Montana State University, Corvalis, MT) were evaluated for the control of bean root rots in a field experiment. Treating bean seeds with isolate AB254 of Ps. fluorescens resulted in an improved seedling establishment, higher bean yield, and lower root rot severity ratings as compared to those of the untreated check treatment. The efficacy of this isolate was equivalent to that of the standard commercial fungicide seed treatments used in this test (Apron + Demosan or Apron + Captan). One isolate of Ps. cepacia also gave promising results and merits re-testing.
Impacts
(N/A)
Publications
|
Progress 01/01/91 to 12/30/91
Outputs
The effects of tillage practices on root rot severity and yield of snap bean were re-evaluated in the same experimental plots used in 1990. Normal fitting and plowing (moldboard) was compared to chisel plowing and rototilling only the planting rows. Emergence and stand counts of seedlings were highest in the normally plowed plots and worst in the rototilled plots. Also, growth weight of plants close to bloom time and yield of beans at harvest were highest in the normally plowed plots and were reduced by the other two tillage practices. Root rot severity ratings were significantly higher in the rototilled and chisel plowed plots. Rhizoctonia, Fusarium, and Thielaviopsis root rot symptoms, in descending order, were evident on the plants at this location. Two biological control isolates of Pseudomonas fluorescens were evaluated as seed treatments on sweet corn and snap beans under artificial field infestation with Rhizoctonia solani and Pythium ultimum. These
isolates were ineffective in improving yield or reducing root rot severity under the prevailing weather and disease conditions at the test location. Also, two preparations of Pseudomonas cepacia (Blue Circle) were found ineffective in reducing root galling or increasing yield of lettuce grown on organic soil heavily infested with Meloidogyne hapla. Samples collected from organic soils naturally infested with M. hapla will be assayed for the presence of native biological control agents against this nematode.
Impacts
(N/A)
Publications
|
Progress 01/01/90 to 12/30/90
Outputs
ClandoSan (consisting of crustacean chitin-protein complex, urea, and organic buffer materials) were re-evaluated as an organic amendment ("biological nematicide") on lettuce grown on organic soil heavily infested with Meloidogyne hapla (Mh, northern root-knot nematode). As in 1989, the marketable weight of lettuce heads growing in the ClandoSan treated plots was higher than the weight of those growing in the fertilizer check plots. However, the ClandoSan treatment did not reduce the root galling (incited by Mh) severity ratings as determined at harvest time. The observed beneficial effect of ClandoSan against Mh may occur shortly after planting perhaps by delaying nematode invasion or may be due to other factors, which needs further documentation. Two formulations of Blue Circle (growth promoting rhizobacteria consisting of selected strains of Pseudomonas cepacia were evaluated as seed treatment on lettuce grown in organic soil. Low incidence or root galling
occurred in the plot area, thus it was not possible to determine if these bacterial preparations had an effect on the nematode. The effects of three tillage practices (moldboard plowing, chisel plowing and rototilling the planting row) on root severity and yield of snap beans were evaluated in the field. Bean plants grown in the rototilled and chisel plowed sections had higher root rot severity ratings and lower yield than those grown in the moldboard plowed sections.
Impacts
(N/A)
Publications
|
Progress 01/01/89 to 12/30/89
Outputs
The efficacy of ClandoSan against plant parasitic nematodes was evaluated on several crops under greenhouse, field microplot, and commercial field conditions. ClandoSan is a product of IGENE Biotechnology, Inc., which has been registered with the EPA as a nematicide for use on many crops including vegetables in 49 states. In greenhouse tests, the addition of ClandoSan at rates of 1 to 3 g/kg soil increased weight of cabbage and table beet seedlings in both nontreated (infested with Heterodera schachtii) and pasteurized field soils. Higher rates of ClandoSan (4 g/kg soil) were phytotoxic to both crops. A field microplot test was conducted to determine the effect of ClandoSan at rates of 1 and 2 T/A for the control of H. schachtii on table beets at four densities (0, 10, 20, and 40 eggs/cc soil). Results obtained suggested that ClandoSan did not improve vigor or yield of beets. In commercial field tests, ClandoSan at 2 T/A increased weight of lettuce heads grown in
organic soil and reduced the number of eggs of Meloidogyne hapla that were recovered from roots. Growth parameters of winter squash, melons, and table beets grown on mineral soils, generally of heavy texture, were not improved by the ClandoSan treatment as compared to those of the appropriate fertilizer checks. The winter squash and melon soils had low level of infestation with lesion nematodes (Pratylenchus spp.), whereas the beet soil was heavily infested with H. schachtii.
Impacts
(N/A)
Publications
|
Progress 01/01/88 to 12/30/88
Outputs
Wild-type and laboratory selected mutants of Laetisaria arvalis that are known for their efficacy against Rhizoctonia solani and Pythium ultimum were maintained and tested as potential biotypes that are producers and nonproducers of laetisaric acid, the antibiotic responsible for the biological control abilities of the antagonistic fungus. Sclerotia maintained dry for many years were observed to be viable and can serve as useful propagules to be deployed in the field. Sclerotia stored at 5 C for up to seven years were 100 percent viable when plated onto growth media. Samples stored at room temperature (21 C) were not viable after 10 years. Previous tests with the latter samples were viable when last tested after seven years storage.
Impacts
(N/A)
Publications
|
Progress 01/01/87 to 12/30/87
Outputs
Mutants of Laetisaria arvalis derived from ultraviolet irradiation were screenedfor antibiotic (8-hydroxy linoleic acid) production against a series of fungal isolates. Growth inhibition and cytoplasmic lyses of Pythium ultimum were used as the standard tests by which the various mutants were compared. Previous studies showed only one mutant exhibiting a decreased zone of growth inhibition. None exhibited enhanced antibiotic production. Subsequent tests with this mutant as well as with other mutants against Verticillium albo-atrum, Phoma betae, Rhizoctonia solani, Fusarium solani, and Mucor racemosus exhibited no differences in inhibition of growth or in lyses of the cytoplasm. Nearly one-half of the original mutants did not survive continued culturing, indicative that deleterious mutant characteristics were created.
Impacts
(N/A)
Publications
|
Progress 01/01/86 to 12/30/86
Outputs
Table beet and snap bean crops are frequently grown rotationally in the same field. A six-year replicated trial dealing with the effect of cover crops and cropping sequences on root rot severity and yield of bean were conducted to access the biological activity of the primary root rotting pathogen of both bean and beet, Pythium sp. Seedling establishment and yield of beans were generally highest in the plots with barley, wheat or rye grain, as compared to those with red clover, oats, rye grass or the fallow plots. Of the seven cropping sequences evaluated, the bean, oat/clover, clover, clover and bean cropping sequence resulted in the highest plant population and marketable yield. Although some differences in root rot severity ratings were observed, they were not statistically significant. Other data collected on the population dynamics of soilborne pathogens, including those of Pythium spp., soil organic mater, soil pH, soil nutrients and others are now being
analyzed. In addition, growing beans or table beets on raised ridges have been shown to reduce Pythium root rot on both crops and increase yield. Under New York conditions, soil moisture is reduced and soil temperature is increased on raised ridges as compared to flat seedbeds.
Impacts
(N/A)
Publications
|
Progress 01/01/85 to 12/30/85
Outputs
We determined that a product of Laetisaria arvalis, 8-hydroxy linoleic acid, waslikely responsible for the antagonistic mechanisms against other fungi (Bowers et al., 1986), thus, we have directed our attention toward antibiotic producing mutants of L. arvalis. Ultraviolet irradiation treatments produced a series of L. arvalis mutants that show variable morphological characteristics. Several mutants demonstrate varying levels of antibiotic production as screened for zones of inhibition on Pythium seeded petri plates. The levels of antibiotic production do not, however, vary enough to use the mutants in a breeding program. To further evaluate the antibiotic producing (or non-producing) mutants, we have developed a second bioassay system using Phytophthora zoospores. Zoospores have been shown to respond to 8-hydroxy linoleic acid at LD50 of 8 ppm. Hyphae of Pythium ultimum also can be used to evaluate for antibiotic production. Both synthetic and naturally
occurring 8-hydroxy linoleic acid and its methyl ester show similar activities. * MARTIN, S.B., ABAWI, G.S., and HOCH, H.C. 1985. Biological control of soilborne pathogens with antagonists. In: Biological Control and Integrated Pest Management Systems. M. Hoy and D.C. Herzog (eds.), Academic Press. PP. 589.
Impacts
(N/A)
Publications
|
Progress 01/01/84 to 12/30/84
Outputs
The effect of soil pH (range 5-8) on the biological control abilities of Laetisaria arvalis was studied in Long Island soil (sandy loam). Greatest control of Pythium-incited damping-off of table beet seedlings occurred at pH 5 and 6. The interrelationship of Laetisaria arvalis, a biological control agent, with Pythium ultimum, was determined in regard to propagule levels and incidence of P. ultimum incited disease of table beet. L. arvalis was added as sclerotia at different densities/gm Pythium-infested soil. Disease incidence and propagule levels of both fungi were determined at timed intervals following planting. To quantitate the propagule level of L. arvalis in natural soil, a wet sieving procedure was developed whereby sclerotia and soil debris were collected on a 60 mesh sieve. The cleaned debris was collected on filter paper via vacuum, partioned into sterilized petri dishes to which 15-20 ml of the sclerotia medium was added. In natural soils, number of
healthy seedlings increased linearly, while recovery of Pythium decreased linearly with increased densities of L. arvalis. In a second soil, which initially contained a lower population of Pythium spp., percentages of healthy seedlings in unamended soil was 40%, whereas soil containing 100 sclerotia/gm soil supported 60% healthy seedlings.
Impacts
(N/A)
Publications
|
Progress 01/01/83 to 12/30/83
Outputs
The propagule level at which Laetisaria arvalis would prevent damping-off and suppress the population of Pythium ultimum was determined in both greenhouse and growth chambers. Between 10 and 100 propagules of L. arvalis/g soil was required for effective disease control. These results correspond well to the density of 30-50 propagules/g soil observed in microplot trials. L. arvalis was utilized as seed treatments and/or incorporated as colonized wheat bran into soil of permanent field microplots to study its efficacy against Pythium-induced diseases of beet. Half the microplots originally treated with L. arvalis in 1982 received another application of the antagonist in 1983. Pythium propagule densities fluctuated in the naturally infested soil, but were suppressed in the L. arvalis-amended treatments. Additional infestation of natural soil with Pythium resulted in a rise in the Pythium propagule level that was maintained for the first 4 months. However, Pythium
levels were modulated to an equilibrium near the original levels of non-amended soil. L. arvalis also suppressed the population of Pythium in the latter treatment. L. arvalis propagule levels were initially increased but later achieved a steady density. Where L. arvalis was incorporated, the value of the graded crop was significantly better than that of the treatments without L. arvalis. Monetary yield for grade no. 1 beets nearly doubled with the addition of L. arvalis.
Impacts
(N/A)
Publications
|
Progress 01/01/82 to 12/30/82
Outputs
Addition of Laetisaria arvalis to both pasteurized and natural soils planted to table beets (Beta vulgaris L.) was highly effective in suppressing reproduction of Pythium ultimum in greenhouse tests. The number of germinable propagules of P. ultimum reached a maximum of approximately 300 and 6,000/g in L. arvalis-amended and nonamended pasteurized soil, respectively. Addition of L. arvalis to natural soil similarly reduced buildup of germinable propagules of low-temperature Pythium spp. The final number of sclerotia of L. arvalis was lower in Pythium-infested natural soil than in pasteurized soil, but was still relatively high (30 sclerotia/g) after 16 wk. Soils that were replanted repeatedly to a host crop for Pythium developed suppressiveness that was characterized by reduced P. ultimum propagule numbers, increased numbers of L. arvalis sclerotia, and lower seedling disease incidence. Fifty permanent field microplots (1.3 m diam, each) were initiated in 1982 to
study the survival of L. arvalis and its long-term effect on P. ultimum. After 9 months, L. arvalis exist in these soils at 91% of the originally introduced level. Under field conditions, L. arvalis sclerotia applied as a seed treatment, protected the beet seed and plant from Pythium-incited diseases. Crop value, percent damping-off and total disease ratings were as good with L. arvalis as with the best fungicide-insecticide seed treatments. L. arvalis has been isolated from Long Island soils.
Impacts
(N/A)
Publications
|
Progress 01/01/81 to 12/30/81
Outputs
Purification and identification of the chemical factor produced by Laetisaria arvalis, that causes lysis of Pythium cytoplasm, has continued. A multistep procedure using HPLC and TLC has now been obtained that yields a reasonably pure compound of low molecular weight (between 100 and 300). The compound is not likely aromatic since it does not absorb UV light, is heat stable, is somewhat polar, and is active at less than 250 ppm (at the present state of purity). To improve effectiveness of beet seed treatments, L. arvalis has been tested in vitro for use in combination with various fungicides, antibiotics, and nutrients. Laetisaria arvalis is tolerant and compatible for use with Previcur, Dexon, Captan, streptomycin, vancomycin, and chloronamphenicol. Pimaricin, Demosan, Terraclor, and Thiram were inhibitory to L. arvalis growth at concentrations of 10 ppm and greater. Beet seedballs pelleted with L. arvalis and various chemicals provided control no better than the
chemicals alone or than the standard chemical treatment of Captan + Dexon. Pelleting of L. arvalis with either chitin, chitosan, or molasses as carbon sources did not increase disease control in preliminary tests.
Impacts
(N/A)
Publications
|
Progress 01/01/80 to 12/30/80
Outputs
A possible mechanism of action for Lactisaria arvailis against Pythium spp. involves the production of an antibiotic. A non-enzymatic, chemical factor from L. avalis hyphae has been extracted with organic solvents and partially purified via liquid column chromatography. The antibiotic activity; in vitro, causes immediate cytoplasmic lysis of Phythium spp. as well as other Oomycetes. L. arvalis added to nontreated field soil or to steam-treated field soil infested with sporangia of Pythium ultimum significantly reduced the buildup of Pythium propagules in treatments planted to beets. However, no significant changes in Pythium population occurred in soils maintained fallow with or without the addition of L. arvalis. Seed treatment with sclerotia of L. arvalis was evaluated for root rot control in two fields. A standard seed treatment of Captan + Dexon was used as a check. The two treatments were planted in replicated rows across the selected fields by cooperating
growers. At one location, there was no siginifcant difference between the two treatments in root rot incidence, seedling establishment, or yield. At the other location, emergence, stand count, and yield data were higher in the Captan + Dexon treatment. Incidence of root rot was low in both fields due to environmental conditions.
Impacts
(N/A)
Publications
|
Progress 01/01/79 to 12/30/79
Outputs
Microplot test - Sclerotia of Laetisaria arvalis (= Corticium sp.) applied as a beet seedball-coating alone and in combination with dexon provided postemergence damping-off control as well as root rot and "healed wound" control at rates significantly better than untreated seed. Sclerotia-coated seed was as effective as dexon-treated seed. Marketable yield was also increased with the L. arvalis seed treatments. Field trials - Laetisaria arvalis applied as seedball-coating and as colonized leaf-meal substrate incorporated into seed furrow. Results not conclusive because of nondisease-related problems. Same treatments repeated in greenhouse trials substantiated earlier effectiveness of L. arvalis as effective agent for control of damping-off diseases.
Impacts
(N/A)
Publications
|
|